Device and method employing shape memory alloy

Abstract

A system for the metering and delivery of small discrete volumes of liquid is comprised of a small or minimal number of inexpensive components. One such component is a movable member, such as a miniature precision reciprocating displacement pump head, which is driven by an actuator that comprises a shape memory alloy material. The operating mechanism of the system is of little or minimal complexity. The system facilitates the precise metering and delivery of the small discrete volumes of liquid. Potential applications for the system include subcutaneous, long-term, automated drug delivery, for example, the delivery of insulin to a person with diabetes. In such an application, the small, simple and inexpensive nature of the invention would allow for its use as both a portable and a disposable system.

1. A diabetes management system for treating a patient, comprising:
 a blood glucose monitor for collecting blood glucose levels in the patient; 
 an insulin pump having a plunger being disposed adjacent a displacement cavity, the displacement cavity having a diaphragm with a wetted surface and a non-wetted surface, the plunger being in contact with the non-wetted surface of the diaphragm; 
 a shape memory alloy wire attached to the plunger to impart reciprocating movement to the plunger; 
 a timing circuit for activating the shape memory alloy wire including an electrical energy storage device for providing electrical energy to the shape memory alloy wire; 
 a reservoir containing a fluid and being in fluid communication with the displacement cavity so that as the shape memory wire imparts movement to the plunger, the diaphragm reacts to the movement of the plunger to expand and thereby pull a predetermined volume of fluid from the reservoir into the cavity; and 
 a remote unit for wirelessly communicating with the blood glucose monitor and the insulin pump. 
 
     
     
       2. The diabetes management system of  claim 1 , wherein the electrical energy heats the shape memory alloy wire to a transitional temperature thereby causing the wire to shorten. 
     
     
       3. The diabetes management system of  claim 2 , wherein the plunger moves a predetermined amount corresponding to a maximum volume within the displacement cavity. 
     
     
       4. The diabetes management system of  claim 1 , wherein the shape memory alloy wire cools and a biasing spring associated with the wire moves the plunger a predetermined amount corresponding to the minimum volume within the displacement cavity. 
     
     
       5. The diabetes management system of  claim 1 , wherein the timing circuit is programmable. 
     
     
       6. The diabetes management system of  claim 1 , wherein the electrical energy storage device is an electrochemical capacitor having a high capacitance and low-equivalent series resistance. 
     
     
       7. The diabetes management system of  claim 1 , wherein the rate of fluid delivery is controlled by varying the period of time between actuations of the shape memory alloy wire. 
     
     
       8. The diabetes management system of  claim 1 , wherein the blood glucose monitor and at least a portion of the insulin pump are disposable with the exception of the electronics including the timing circuit and the shape memory alloy wire. 
     
     
       9. The diabetes management system of  claim 1 , wherein the insulin pump and the timing circuit are integrated into a single housing. 
     
     
       10. The diabetes management system of  claim 9 , wherein the insulin pump is disposable and the shape memory alloy wire, timing circuit, and electrical energy storage device are reusable. 
     
     
       11. The diabetes management system of  claim 1 , wherein the diaphragm is elastomeric. 
     
     
       12. The diabetes management system of  claim 11 , wherein the plunger has a flat head for attachment to the non-wetted surface of the elastomeric diaphragm. 
     
     
       13. The diabetes management system of  claim 12 , wherein as the shape memory alloy wire is heated by electrical energy from the electrical energy storage device, the wire shortens and moves the plunger in a first direction thereby pulling on the non-wetted surface of the diaphragm and pulling insulin out of the reservoir and into the displacement cavity. 
     
     
       14. The diabetes management system of  claim 13 , wherein as the shape memory alloy wire cools, a biasing spring moves the plunger in a second direction thereby pushing the plunger on the non-wetted surface of the diaphragm to push insulin out of the displacement cavity and into the patient. 
     
     
       15. The diabetes management system of  claim 1 , wherein the insulin reservoir is collapsible. 
     
     
       16. The diabetes management system of  claim 1 , wherein the insulin pump includes an electrical energy source. 
     
     
       17. The diabetes management system of  claim 16 , wherein the electrical energy source is a replaceable battery. 
     
     
       18. The diabetes management system of  claim 17 , wherein the battery is substantially electrically isolated from the shape memory alloy wire. 
     
     
       19. The diabetes management system of  claim 18 , wherein the battery provides electrical energy to the electrical energy storage device. 
     
     
       20. The diabetes management system of  claim 19 , wherein the electrical energy storage device is a capacitor. 
     
     
       21. The diabetes management system of  claim 17 , wherein the battery provides electrical energy to the timing circuit. 
     
     
       22. The diabetes management system of  claim 21 , wherein the timing circuit is a programmable digital timing circuit. 
     
     
       23. The diabetes management system of  claim 22 , wherein the timing circuit includes a transistor switch. 
     
     
       24. The diabetes management system of  claim 23 , wherein the electrical energy storage device is a capacitor. 
     
     
       25. The diabetes management system of  claim 24 , wherein the battery and the capacitor are connected to each other in parallel and are connected to the shape memory alloy wire through the transistor switch. 
     
     
       26. The diabetes management system of  claim 25 , wherein the battery charges the capacitor with electrical energy when the transistor switch is open. 
     
     
       27. The diabetes management system of  claim 26 , wherein the capacitor provides electrical energy to the shape memory alloy wire when the transistor switch is closed. 
     
     
       28. The diabetes management system of  claim 1 , wherein the shape memory alloy wire is up to 40 mm long. 
     
     
       29. The diabetes management system of  claim 1 , wherein the shape memory alloy wire is 125 microns in diameter. 
     
     
       30. The diabetes management system of  claim 1 , wherein the plunger is attached to the shape memory alloy wire. 
     
     
       31. The diabetes management system of  claim 1 , wherein the plunger pumps 0.1 microliter of insulin into the patient per each pump cycle. 
     
     
       32. The diabetes management system of  claim 31 , wherein the insulin pump has an effective maximum of 3000 cycles. 
     
     
       33. The diabetes management system of  claim 1 , wherein the timing circuit generates an electrical pulse duration lasting about 0.15 seconds. 
     
     
       34. A diabetes management system for treating a patient, comprising:
 a blood glucose monitor for collecting blood glucose levels in the patient; 
 an insulin pump having a plunger being disposed adjacent a displacement cavity, the displacement cavity having a diaphragm with a wetted surface and a non-wetted surface, the plunger being in contact with the non-wetted surface of the diaphragm; 
 a nickel-titanium shape memory alloy wire having a high transition temperature for transforming to a high temperature phase, and a low transition temperature for transforming to a low temperature phase, wherein the wire is attached to the plunger to impart reciprocating movement to the plunger via phase transformations; 
 a timing circuit for activating the shape memory alloy wire including an electrical energy storage device for providing electrical energy to the shape memory alloy wire to thermally transform the wire from the low temperature phase to the high temperature phase; 
 a reservoir containing a fluid and being in fluid communication with the displacement cavity so that as the shape memory wire imparts movement to the plunger, the diaphragm reacts to the movement of the plunger to expand and thereby pull a predetermined volume of fluid from the reservoir into the cavity; and 
 a remote control unit wirelessly communicating with the blood glucose monitor and the insulin pump. 
 
     
     
       35. The diabetes management system of  claim 34 , wherein the electrical energy heats the shape memory alloy wire to a transitional temperature thereby causing the wire to shorten. 
     
     
       36. The diabetes management system of  claim 35 , wherein the plunger moves a predetermined amount corresponding to a maximum volume within the displacement cavity. 
     
     
       37. The diabetes management system of  claim 34 , wherein the shape memory alloy wire cools and a biasing spring associated with the wire moves the plunger a predetermined amount corresponding to the minimum volume within the displacement cavity. 
     
     
       38. The diabetes management system of  claim 34 , wherein the timing circuit is programmable. 
     
     
       39. The diabetes management system of  claim 34 , wherein the electrical energy storage device is an electrochemical capacitor having a high capacitance and low-equivalent series resistance. 
     
     
       40. The diabetes management system of  claim 34 , wherein the rate of fluid delivery is controlled by varying the period of time between actuations of the shape memory alloy wire. 
     
     
       41. The diabetes management system of  claim 34 , wherein the blood glucose monitor and at least a portion of the insulin pump are disposable with the exception of the electronics including the timing circuit and the shape memory alloy wire. 
     
     
       42. The diabetes management system of  claim 34 , wherein the insulin pump and the timing circuit are integrated into a single housing. 
     
     
       43. The diabetes management system of  claim 42 , wherein the insulin pump is disposable and the shape memory alloy wire, timing circuit, and electrical energy storage device are reusable. 
     
     
       44. The diabetes management system of  claim 34 , wherein the diaphragm is elastomeric. 
     
     
       45. The diabetes management system of  claim 44 , wherein the plunger has a flat head for attachment to the non-wetted surface of the elastomeric diaphragm. 
     
     
       46. The diabetes management system of  claim 45 , wherein as the shape memory alloy wire is heated by electrical energy from the electrical energy storage device, the wire shortens and moves the plunger in a first direction thereby pulling on the non-wetted surface of the diaphragm and pulling insulin out of the reservoir and into the displacement cavity. 
     
     
       47. The diabetes management system of  claim 46 , wherein as the shape memory alloy wire cools, a biasing spring moves the plunger in a second direction thereby pushing the plunger on the non-wetted surface of the diaphragm to push insulin out of the displacement cavity and into the patient. 
     
     
       48. The diabetes management system of  claim 34 , wherein the insulin reservoir is collapsible. 
     
     
       49. The diabetes management system of  claim 34 , wherein the insulin pump includes an electrical energy source. 
     
     
       50. The diabetes management system of  claim 49 , wherein the electrical energy source is a replaceable battery. 
     
     
       51. The diabetes management system of  claim 50 , wherein the battery is substantially electrically isolated from the shape memory alloy wire. 
     
     
       52. The diabetes management system of  claim 51 , wherein the battery provides electrical energy to the electrical energy storage device. 
     
     
       53. The diabetes management system of  claim 52 , wherein the electrical energy storage device is a capacitor. 
     
     
       54. The diabetes management system of  claim 50 , wherein the battery provides electrical energy to the timing circuit. 
     
     
       55. The diabetes management system of  claim 54 , wherein the timing circuit is a programmable digital timing circuit. 
     
     
       56. The diabetes management system of  claim 55 , wherein the timing circuit includes a transistor switch. 
     
     
       57. The diabetes management system of  claim 56 , wherein the electrical energy storage device is a capacitor. 
     
     
       58. The diabetes management system of  claim 57 , wherein the battery and the capacitor are connected to each other in parallel and are connected to the shape memory alloy wire through the transistor switch. 
     
     
       59. The diabetes management system of  claim 58 , wherein the battery charges the capacitor with electrical energy when the transistor switch is open. 
     
     
       60. The diabetes management system of  claim 59 , wherein the capacitor provides electrical energy to the shape memory alloy wire when the transistor switch is closed. 
     
     
       61. The diabetes management system of  claim 34 , wherein the shape memory alloy wire is up to 40 mm long. 
     
     
       62. The diabetes management system of  claim 34 , wherein the shape memory alloy wire is 125 microns in diameter. 
     
     
       63. The diabetes management system of  claim 34 , wherein the plunger is attached to the shape memory alloy wire. 
     
     
       64. The diabetes management system of  claim 34 , wherein the plunger pumps 0.1 microliter of insulin into the patient per each pump cycle. 
     
     
       65. The diabetes management system of  claim 64 , wherein the insulin pump has an effective maximum of 3000 cycles. 
     
     
       66. The diabetes management system of  claim 34 , wherein the timing circuit generates an electrical pulse duration lasting about 0.15 seconds. 
     
     
       67. A diabetes management system for treating a patient, comprising:
 a blood glucose monitor for collecting blood glucose levels in the patient; 
 an insulin pump having a plunger being disposed adjacent a displacement cavity, the displacement cavity having a diaphragm with a wetted surface and a non-wetted surface, the plunger being in contact with the non-wetted surface of the diaphragm; 
 a nickel-titanium shape memory alloy wire having a high temperature phase and a low temperature phase attached to the plunger, wherein the phase changes impart reciprocating movement to the plunger; 
 a timing circuit for activating the shape memory alloy wire including an electrical energy storage device for providing electrical energy to the shape memory alloy wire to thermally transform the shape memory alloy wire from the low temperature phase to the high temperature phase; 
 a battery and capacitor for powering the timing circuit; 
 a reservoir containing a fluid and being in fluid communication with the displacement cavity so that as the shape memory wire imparts movement to the plunger, the diaphragm reacts to the movement of the plunger to expand and thereby pull a predetermined volume of fluid from the reservoir into the cavity; and 
 a remote unit for wirelessly communicating with the blood glucose monitor and the insulin pump.